Sound amplifier



Oci. '11, 1927. 1,644,795

L. STEVENS SOUND AMPLIFIER Filed April 15, 1925 Patented a. 11, 1927.

UNITED STATES LESLIE STEVENS, OF GLEN RIDGE, NEW JERSEY.

scum) AMPLIFIER.

Application filed Apri1-15, 1925. Serial No. 23,172.

This invention relates to sound amplifiers, and particularly to the type adapted for use with radio receiving apparatus. The pr ncipal object of this invention is to provide a new and improved construction for devlces of this character by means of which the tonal qualities of the instrument are improved. A further object is to construct an amplifier of a plurality of parts or sections of non-resonant material assembled in a novel manner to rovide an instrument of restricted dimens1ons having a relatively long tortuous passage for the sounding air column.

As an example, an'approved embodiment of the invention in a radio loud speaker is shown in the accompanying drawings, in which Fig. 1 is a front elevation of the instrument;

Fig. 2 is a section on the line 2-2 of Fig. 1- and Fig. 3 is a section on the line 33 of Fi 2. g the particular form of my invention illustrated, the amplifier comprises an outer casing, or shell, consisting of a rear member 10 and a front member 11, each shown as having a dished central portion and a cylindrical peripheral flange 10 and 11', respectively, one of said flanges fitting telescopically within the other. The two casing members are held together in any suitable manner, as, for example, by means of bolts 12 which also serve to secure the casing to a supporting base 13, or they ma be cemented together. A telephone or lou s eaker unit 14, which may be of any suita le type or construction, is secured within a recess 15 provided at the central portion of the-rear member 10, the base of said recess being provided with a central aperture to receive the outlet neck 16 of said unit. The unit 14 may be secured to the casing in any suitable mannor, a cap 17, which bridges the recess 15 and is fastened to the casing by screws 18, being shown in the illustrated example for this purpose.

Fitted tightly within the outlet neck 16 of the unit 14 is the small rear end of a short tubular member or frusto-conical megaphone 20. The larger outer extremity of said megaphone is tapered or inclined to provide a joining sur ace, to which is cemented at 21 a similar surface formed on the rearwardly turned neck 22 at the front end of a flaring bell-shaped member 25. This member has its rear end curved outwardly as indicated at 26 and its outer edge is fitted and cemented as at 27 to the inner curved face of the rear casing member 10. A filling piece, which for convenience of manufacture is constructed of two parts 28 and 29 connected together by a cemented joint 30 to form a continuous unitary structure, is interposed between the member 25 and the outer casing, and is secured to the member 25 by any suitable means such as the screws 31.

In order to hold the filling piece in spaced concentric relationship to the member 25, a plurality of abutment screws 32are secured to said member and form supports for said filling piece. The filling piece is so shaped and the length of the "screws 32 so proportioned that the rearwardly extending and outwardly flaring annular passage 33 formed between the filling piece and member 25 widens gradually ir'romthe central portion -"outward to the periphery. The central portion of the filling piece is shapedto provide a curved annular recess or channel 34 the inner bounding surface of which terminates in a, conical polnt 35 in axial alignment with the megaphone 20., the walls of said channel iormin curved deflecting surfaces, free from s arp bends or angles, to direct the sound waves from the megaphone outwardl and rearwardly into the rearwardl exten ing passage 33. At its rear end the filling piece 28, 29 is curved, as at 36, for cooperati with the outwardly curved end 26 of the bell member 25 to form a curved lateral extension of the passage 33 and direct the sound waves into the forwardly extending annular passage'37 formed between the outer casing and the outer wall of the filling piece. This outer wall of the filling piece is turned inwardl to cause the passage 37 to be of adua y increasing cross-sectional area 109 om the rear of the casing towards the plurality of a ertures 38 formed in the front casing mem er 11. The parts of the am lifier are constructed and arranged to provi e a long tortuous passage, or. conduit, of gradually increasing cross-sectional area for the s'oundin column of air contained therein. This con uit comprises the forward] extendin passage, defined by the megaplione 20; t e rearwardly extending annular passage 33, bounded by the member 25 and the filling piece part 28; and the forwardly extending annular passage 37, bounded by the outer casing and the filling piece. The rate of increase of cross-sectional area of the sound amplifying conduit should for best results be greater than it would be in that portion of the conduit formed by ,the passage 33 if the walls of such passage were the same distanceapart at all points, and the distance between the walls of this passage 33 is therefore made to increase gradually from the central portion outward to the periphery, so that the cross-sectional area of the passage increases at a rate greater than that due to the increase in the diameter of the passage. The reversals of the direction of travel of the sound waves in passing through the sound amplifying passage or conduit are effected by the curved surfaces of the annular recess or channel 34 and the curved surfaces at the rear of the member 25 and the filling and 11 and the sound directing members 20,-

25, 28 and 29 are made of non-resonant or but slightly resonant material so that no distortion of the sound will occur due to vibration or rattling of the parts of theamplifier. A suitable material having the desirable non-resonant properties is buckram or other stiff woven fabric impregnated with any suitable cement or sizing and molded to the desired shape. Two or more layers of the fabric are preferably employed, stiflened with sizing and shaped and pressed between dies to the desired configuration while the sizing is moist. For convenience in manufacture, the megaphone 20, the member 25 and the filling piece parts 28 and 29 are shaped or molded separately and are then connected, as shown, by the cemented joints 27 and 30.

Various modifications may be made in the construction shown without departing from the invention as set forth in the claims, and sound amplifiers embodying features of the invention may be used for amplifying sound vibrations from sources other than radio telephone units. A

What is claimed is:

1. A sound amplifier, comprising a pair of sound directing members arranged in spaced concentric relationship to form a tortuous passage, each of said members being constructed of a-plurality of truncated substantially cone-shaped members connected together to form continuous curved surfaces, whereby the tortuous passage is free from sharp edges and corners, and said sounddirecting members being of such shape that the tortuous passage is of gradually increas ing cross-sectional area throughout its length.

2. A sound amplifier, comprising an outer casing apertured for the emission of sound, and a pair of sound-directing members arranged in spaced concentric relationship within said casing to form a tortuous passage, each of said members being formed of two truncated substantially cone-shaped members of non-resonant material and connected together to form uninterrupted curved surfaces whereby the tortuous passage is free from sharp edges and corners, and said sound-directing members being of such shape that the tortuous passage increases in crosssectional area gradually throughout its length toward the apertured wall of the casing and that the rate of increase in crosssectional area of the passage is greater than that due to the increase in diameter of the annular outwardly flaring portions of the passage.

3. A sound amplifier, comprising an outer casing having its front wall provided with sound emission openings and its rear wall provided with means to secure a sound reproducing unit thereto, a sound-directing member in communication with said unit consisting of a forwardly-flaring tubular member and a rearwardly extending bell-shaped member connected together to form a continuous unitary structure, and a filling piece ,mounted concentrically between said casing and bell-shaped member and forming therewith a rearwardly extending and outwardly flaring annular passage which widens gradually from the central portion outward to the periphery and a forwardly extending annular passage to direct. the sound to said emission openings.

4. A sound amplifier, comprising an outer casing having its front wall provided with sound emission openings and its rear wall provided with means to secure a sound reproducing unit thereto, a sound-directing member in communication with said unit consisting of a forwardly-flaring tubular member and a rearwardly extending bellshaped member onnected together to form a continuous unitary structure, a filling piece mounted between said casing and bellshaped member and defining therewith a rearwardly extending and outwardly flaring annular passage and a forwardly extending annular passage, and means for holding said filling piece in spaced concentric relationihip with said casing and bell-shaped mem- 5. A sound am lifier, comprising an outer circular casing wliose axial dimension is less than its diameter, said casing having a front wall provided with sound emission openings and a rear wall provided with means to secure a sound reproducing unit thereto; and

means within said casing forming a long tortuous annular conduit for a sounding air column whose cross-sectional area increases gradually from said unit towards said sound emission openings, said means consisting of a plurality of concentrically arranged parts constructed of substantially non-resonant material and interconnected to form a unitary structure.

6. A sound amplifier, comprising an outer circular casing constructed of substantially non-resonant material and having an axial dimension less than its diameter, said casing having its rear wall provided with an aperture adapted to have connected therewith a sound reproducin unit, and said casing being further provided with sound emission openings; and a pluralit of sound-directing members constructed 0 substantially nonresonant material concentrically arranged within said casing to provide a long tortuous annular conduit for a sounding air column whose cross-sectional area increases gradually from said aperture. toward said sound emission openings, said members comprising a short forwardly extending megaphone in communication with said aperture, a rearwardly extending bell-shaped member secured to said megaphone, and a filling piece interposed between said bell-shaped member and the casing and having its outer extremity curved outwardly and forwardly to 01m with the outer portion of the bell-shaped member an outwardly and forwardly curving portion of the conduit.

7 A sound amplifier, comprising an outer circular casing constructed of substantially non-resonant material and having an axial dimension less than its diameter, said casing having its rear wall provided with an aperture adapted to have connected therewith a sound reproducing unit, and said casing being further provlded with sound emission openings, and a pluralit of sound-directing members constructed 0 substantially nonresonant material concentrically arranged within said casing to provide a long tortuous annular conduit for a sounding air column, said members comprising a short for wardl extending megaphone in communication wit said a erture, a rearwardly extending bellshape member secured to said megaphone. and a filling piece interposed between said bell-shaped member and the casin said filling piece and bell-sha ed member eing provided with curved de ecting Surfaces to produce successive reversals in the direction of said conduit free from sharp corners or angles.

8. A sound amplifier, comprising an outer circular casing constructed of substantially non-resonant material and having an axial dimension less than its diameter, said casing having its rear wall provided with an aperture adapted to have connected therewith a sound reproducing unit, and said casing being further provided with sound emission openings; and a plurality of sound-directing members constructed of substantially nonresonant material concentrically arranged within said casing to provide a long tortuous annular conduit for a sounding air column, said members comprising a short forwardly extending megaphone in communication with said aperture, a rearwardly extending 'bel1-' shaped member secured to said megaphone, and a filling piece interposed between said bell-shaped member and said casing and constructed of a plurality of pieces of non-resonant material cemented together to form uninterrupted curved surfaces.

9. A sound amplifier, comprising an outer circular casing constructed of substantially non-resonant material and having an axial dimension less than its diameter, said casing having its rear wall provided with an aperture adapted to have connected therewith a sound reproducing unit, and said casing being further provided with sound emission openings; and a pluralit of sound-directing members constructed 0 substantially nonresonant material concentrically arranged within said casing to provide a long tortuous conduit for a sounding air column, said members comprising a short forwardly extending megaphone in communication with said aperture, a rearwardly extending bell-shaped membersecured to said megaphone, and a filling piece interposed between said bellshaped member and said casing and constructed of a plurality of pieces of non-resonant material cemented together to form uninterrupted curved surfaces, said filling piece, casing and bell-shaped member being shaped to produce SllCCBSSlVG reversals in direction of said conduit free from sharp corners or angles.

10. A sound amplifier, comprising an outer casing constructed of substantially non-resonant material and'having an axial dimension less than its diameter, and means to define within said casing a long tortuous conduit for a soundin column of air, said means comprising a s ort megaphone which defines a forwardly extending passage, a bell-shaped member connected to said me phone to form therewith a continuous unitary structure, and a filling piece secured in spaced concentric relationship between said member and the outer casing, said filling piece cooperating with said member to form a rear wardly extending passage and with said casin to form a forwardly extending passage, anl said filling piece and said member being formed with curved sound-directing surfaces to produce successive reversals of said conduit between said passages without sharp bends or angles.

11. A sound amplifier, comprising an outer casing provided with a sound emission opening, a pair of sound directing members arbers being formed of two truncated substanranged in spaced concentric relationshifi tially cone-shaped members connected towithin said casin and cooperating with eac gether to form continuous curved surfaces. 10 other and with semi casing to form a tortuous In testimony whereof I have hereunto set annular sound-amplifying passage whose my hand.

cross-sectional area increases graduallytowards said opening, and each of said mem- LESLIE STEVENS. 

